This invention relates to the field of integrated circuit fabrication. More particularly, this invention relates to a process of performing contaminant sensitive structures on a substrate.
A variety of different materials are typically used in integrated circuit fabrication processes. Many of these materials are highly susceptible to various contaminants. In addition, some processes, at intermediate points, create sites or structures that are very susceptible to contamition. For example, when trenches or holes are etched into dielectric films, the dielectric films tend to be extremely susceptible to contaminants in the atmosphere such as oxygen, nitrogen, rare gases, hydrocarbons, water vapor and other atmospheric contaminants. When exposed to such, the etched portions of the dielectric layer tend to attract such contaminants and can subsequently release the contaminants, such as by outgassing, which tends to have adverse affects on the subsequent processing of the substrate.
In the specific case of low dielectric constant materials, which tend to be porous in nature, the adsorption of contaminants tends to be even greater. Thus, when a low dielectric constant material is etched, the etched portions tend to adsorb contaminants. Then, when a thin material layer is subsequently deposited over the etched portions, such as when a diffusion barrier is formed in a via, the contaminants absorbed in the low dielectric constant material in the area of the etched via tend to outgas and interfere with the uniform and desirable deposition of the deposited layer. This condition tends to cause problems with the integrated circuit, such as barrier layers that are porous or otherwise defective, and which do not exhibit the desired barrier properties.
As a more specific example, when a titanium adhesion layer is deposited in an etched low dielectric constant via, and then the titanium adhesion layer is followed by a titanium nitride diffusion barrier layer, and then the titanium nitride diffusion barrier layer is followed by a tungsten plug deposition, the tungsten plug deposition tends to not fill properly due to moisture absorption and subsequent outgassing by the intermediate layers.
What is needed, therefore, is a method of forming structures on a substrate where the substrate and the various layers are processed in a manner that substantially inhibits moisture absorption and undesired outgassing.
The above and other needs are met by a method of processing a substrate, where the substrate is transferred from an ambient environment into a clean environment. The substrate is heated to at least a first temperature within the clean environment, and then maintained at no less than the first temperature within the clean environment. The substrate is selectively transferred within the clean environment to more than one processing chambers, and processed in the more than one processing chambers. The substrate is transferred from the clean environment into the ambient environment.
By maintaining the temperature of the substrate to at least the first temperature during processing of the substrate within the clean environment, the substrate tends to absorb a reduced amount of contaminants, such as moisture. Thus, because a reduced amount of contaminants such as moisture are adsorbed, there is a commensurately reduced amount of undesirable outgassing from the substrate. Therefore, the layers deposited on the substrate tend to exhibit improved characteristics, such as adhesion.
In various preferred embodiments of the invention, the step of maintaining the substrate at no less than the first temperature within the clean environment is accomplished in different ways. In one embodiment all of the clean environment is heated to at least the first temperature. In another embodiment the substrate is transferred and processed quickly through the more than one processing chambers within the clean environment so that the substrate does not have time to cool below the first temperature. In a third embodiment the substrate is heated to at least the first temperature within each of the more than one processing chambers, and the substrate is transferred quickly between the more than one processing chambers within the clean environment so that the substrate does not have time to cool below the first temperature between the more than one processing chambers.
The first temperature is preferably at least about 150 centigrade, and most preferably between about 150 centigrade and about 350 centigrade. Preferably the pressure within the clean environment is reduced to a base pressure of between about 10xe2x88x927 torr and about 10xe2x88x929 torr. Most preferably the pressure within the more than one processing chambers is selectively adjusted while processing the substrate in the more than one processing chambers.
In a most preferred embodiment the step of processing the substrate in the more than one processing chambers includes heating the substrate under a vacuum in a degassing chamber, etching the substrate in an etch chamber, depositing a layer of titanium in a first deposition chamber, and depositing a layer of titanium nitride in a second deposition chamber.